Relays are known. They have contact bridges that cooperate with associated counterpart contacts in order to close a load current circuit that is to be switched. Relays for internal combustion engine starters, because of the high currents to be switched, have contact bridges, which because of the high current-carrying capacity required have a large conductor cross section. Because of the large conductor cross section, the contact bridges are embodied as substantially solid. In the prior art, it is known to position such contact bridges vertically to the switching axis on a contact bridge holder that makes a defined switching actuation possible by means of a compression spring (spiral spring) and a contrarily acting restoring spring. The contact bridge is electrically disconnected by an insulating bush from the components that support it, in particular the contact bridge holder and the compression spring. These known embodiments are known as externally sprung contact systems.
Solid contact bridges as described above tend to recoil upon closure of the contact. In the course of the abrupt switching event (contact closure), ionization of the gas molecules surrounding the respecting contacts and sparking occur because of the high current intensities. This causes burnoff of the contact faces, and under some circumstances, especially with worn contacts, it causes the contacts to fuse to one another in the closed state, because of the severe heating caused by the spark. In that case, the relay contact can no longer be opened. In the case of the aforementioned recoiling event, contact interruptions occur as well as (because of the recoiling event) increased sparking. It is also disadvantageous in these constructions that contact wear, for instance from burnoff, worsens the contact position; in other words, the contact faces of the contact bridge and of the associated counterpart contacts no longer touch over their full surface. With increasing wear of the contact faces, particularly from burnoff (loss of material from the above-described sparking), the available contact face, or in other words the surface area at which the contacts in fact close reliably, decreases; at the same time, the air gap that exists in the open state of the relay between the contact bridge and the counterpart contact becomes larger. Another disadvantage of the prior art is that the cylindrical contact compression spring in conventional contact systems occupies a relatively large amount of installation space and disadvantageously determines the axial structural length of the relay. The axial structural length is understood to mean the elongation of the relay along the switching axis that receives the contact bridge (that is, perpendicular to the elongation of the contact bridge and along the actuation path).